The present invention relates to a suspension device comprising in- and an out-configurations, respectively, for a vehicle. The present invention also relates to a method for providing a damping and/or springing action with in- and out-configurations of a vehicle. The present invention further relates to a vehicle. The present invention also relates to a computer programme and a computer programme product for performing the method.
Road holding, running characteristics and comfort are important parameters of vehicles such as cars, military vehicles, trucks and the like. In order to improve road holding, running characteristics and comfort, vehicles are equipped with suspensions systems, which is arranged to protect the vehicle, passengers and load from damage and wear. A suspension system comprises spring members for supporting the vehicle at the correct level and absorbing impacts such that irregularities on the ground do not propagate to the vehicle body, and damp members for putting out vibrations, roll and rocking of the vehicle body.
During cornering, for example, the vehicle rotates about its own roll axes, i.e. the vehicle tends to incline. By so-called hydro-pneumatic springs, the force of the springs level out during spring expansion, as opposed to a helical spring, which has a linear spring curve in which the force approaches zero by spring expansion. The high pre-load of hydro-pneumatic springs results in that in the spring expansion position there still is a relatively large spring force of the hydro-pneumatic spring, which results in the fact that the vehicle will incline to a greater extent during, for example, cornering when roll occurs.
By using so-called stabilizers, i.e. a suspension attachment in the form of a bar connecting opposite wheels of the vehicle, a reduced inclination without stiffening of the vertical suspension is conceivable, facilitating improved running characteristics with a relatively good comfort. A problem with the use of a stabilizer is that it transfers the power of a bumping wheel to the opposite wheel, wherein shaking from side to side occurs, which increases with the diameter and stiffness of the stabilizer, and, where applicable, may lead to lifting of the inner wheels by heavy cornering. Due to the high pre-load of hydro-pneumatic springs, strong stabilizers are required, which results in them having to be excluded in cross-country vehicles in certain cases since the traversability in terrain is heavily reduced.
Lately more active suspension systems have been developed which adapt to the present state of the vehicle. A so-called semi-active suspension system is arranged to regulate the damping while the spring has a non-variable spring constant, or alternatively is arranged to regulate the spring constant where the damping is kept constant. An active spring system is arranged to regulate both damping and spring action. Stabilizers may be replaced by semi-active/active systems in which the spring is actively controllable. A problem with such semi-active/active suspension systems is that variable damping action by compression leads to, when the damping action is increased, the possibility of the wheel starting to bounce when the roadway is uneven, such that the vehicle loses its grip.
U.S. Pat. No. 4,153,237 discloses a hydro-pneumatic damping device comprising a damper with a manually adjustable low-speed damping on the return and compression, and manually adjustable high-speed damping on return. The suspension device does not have an active damp valve.
U.S. Pat. No. 4,720,085 discloses a damping device with both adjustable compression and return, in which adjustment of compression and return is done by means of an electric motor.
U.S. Pat. No. 4,159,106 discloses a damping device with a damper having a pressure dependent return damping action, in which regulation of the damper is done mechanically automatically. The damping of the damping device is not controllable.